Reciprocating downhole pumps have been used in the oil and gas industry for years to raise oil to the surface. In order to direct the oil flow at the surface of the well, a stuffing box is employed to seal around the reciprocating rod string. Stuffing boxes are commonly used for sealing with a reciprocating rod string.
Progressive cavity pumps rely upon the rotary action of the rod string rather than reciprocating action to power the downhole pump. Stuffing boxes for rotating rod strings commonly use conventional packing material as the sealing element, although some designs employ Chevron-type sealing elements.
The failure of a stuffing box is environmentally damaging and costly. Most often, failure results in spillage of oil at the well site, and well sites are thus commonly subject to expensive cleanup operations to eliminate hydrocarbons around the area of a well. Stuffing boxes also require a fairly high maintenance, and operators frequently are scheduled to check operating stuffing boxes to ensure that there are no leaks, to eliminate or minimize any leakage that is occurring, and to replace stuffing boxes when necessary. Leakage of a stuffing box thus represents a significant cost of recovering oil from wells which are driven by a downhole pump and a powered sucker rod.
U.S. Pat. No. 4,372,379 discloses a drive assembly for powering a downhole rotary pump. The drive motor is not directly over the wellhead, and FIG. 3 discloses the bearings and seals for sealing fluid within the wellhead. U.S. Pat. No. 4,647,050 discloses a stuffing box for a sucker rod pump, and U.S. Pat. No. 5,217,068 discloses another version of a stuffing box for a rotary rod string. U.S. Pat. No. 5,327,961 discloses a drive head for a rotary downhole pump.
U.S. Pat. No. 5,343,944 discloses a self aligning stuffing box for a pump-jack unit. U.S. Pat. No. 5,567,138 discloses a technique for limiting eccentric deviations of a rotating rod string in a pumping application. U.S. Pat. No. 5,791,411 discloses a wellhead stuffing box for a rotating rod string. U.S. Pat. No. 5,865,245 discloses a stuffing box gland for use with a rod string. U.S. Pat. No. 6,637,509 discloses a wellhead stuffing box support assembly positioned between a production pumping tree and a stuffing box of a wellhead.
U.S. Pat. No. 6,843,313 discloses a pump drive head with a stuffing box, and U.S. Pat. No. 7,044,217 discloses a stuffing box for a PC pump drive. U.S. Pat. No. 7,055,593 discloses a stuffing box with packing cones for a seal.
The disadvantages of the prior art are overcome by the present invention, and an improved sealed drive for powering a rotating sucker rod string which drives a downhole progressive cavity pump is hereinafter disclosed.